Black rot is a disease caused by bacterial infection. Use mesomycin, or acetozolin, or polyantimycin, or agricultural streptomycin, or octostrobin acetate, or Chlorobromoisocyanuric acid, or copper chloride, or copper thiophene, or copper thiophene, or copper quinoline, or copper hydroxide, or cuprous oxide, or copper oxychloride, or copper metal frost, or complex Copper ammonia or copper rosinate are very effective in controlling the disease. Spraying the leaves every 7 to 10 days after the onset of the disease and spraying 2 to 3 times continuously can control the disease and restore the diseased plants to normal growth.